The present invention relates to the preparation of oxide/metal composite materials comprising an oxide phase and a metal phase.
The oxide/metal composite materials, which comprise 10 to 80% of metal phase and 90 to 20% of ceramic phase consisting essentially of oxides, have at one and the same time the properties of each the constituent phases, that is to say a good chemical stability, a high hardness, a high melting point, a good ductility and a good break strength.
The heretofore known methods of production of these materials, however, presents difficulties associated with the problem of wetting between the metal phase and the ceramic phase. This problem arises during the high temperature sintering operation which follows the step of grinding and mixing the initial ceramic and metal powders.
Attempts have been made to overcome these difficulties by using surface-active metals, preferably in the form of a pulverulent compound which can be decomposed by the action of heat (European Patent No. 0,277,450).
The present inventors have now developed a process for the preparation of oxide/metal composite materials by in situ formation of the oxide.
This process leads to a better bond between the oxide phase and the metal phase, which in some cases is reflected in a reciprocal solubility of the metal and oxide constituent elements, while ensuring a homogeneous distribution of the various phases in the powders obtained.